Much of the research on sexual attitudes has focused on biological sex as a predictor variable. This work has consistently demonstrated that men are more permissive in attitudes toward casual sex than are women. Less is known, however, about how other individual difference variables may shape sexual attitudes. In this research, we considered whether self-construal (whether one believes that others are or are not part of their self-concept) influences people’s attitudes toward casual sex. Specifically, we posited that an independent self-construal is positively related to, and an interdependent self-construal is negatively related to, sexual permissiveness. Two cross-sectional studies (ns = 517 and 212) yielded support for these hypotheses. We further considered autonomy as a potential process variable. A mediation analysis revealed that self-construal was related to autonomy, which in turn positively predicted sexual attitudes and drove this association. We integrate these findings into the literature on sexual attitudes and discuss theoretical insights derived from our findings.